Abstract
This experiment investigated the allometric development of intramuscular (imf), subcutaneous, and intermuscular fat in Australian Angus heifers and steers a. Steers (90) heifers (75) were fed a grain based ration and randomly allocated to a slaughter weight in the range 200kg to 450kg carcass weight. Body composition was estimated from a 6 rib dissection (5-10) and imf content was estimated on of m. longissimus thoracis et lumborum (LTL). Analysis of the results using general linear modelling (SAS) showed that at any given level of estimated total body fatness, steers had a significantly higher level of intramuscular fat (P < 0.0001) when compared to heifers, though at the same carcass weight there was no significant difference (P >0.05). There was a significantly linear increase (P <0.0001) in imf of the LTL as proportion of total rib fat. As carcass weight increased there was a significant increase in the ratio of gms fat in the LTL/gms of total body fat (P < 0.0001), although the r2 was low (r2=0.121), indicating that intramuscular fat tended to develop more strongly as the carcass weight increased. It can be concluded that steers are more efficient than heifers with respect to accumulation of imf, as they have a higher level of imf at the same total carcass fatness. In addition intramuscular fat accumulation occurred primarily in parallel with total body fat synthesis.